Draft regulating device for orchard heaters



3 Sheetrs-Sheet 1 July 21, 1942.

w. c. scHl-:u ET AL DRAFT REGULATING DEVICEv FOR ORCHARD HEATERS Filed sept. 2, 19:59

July 21, 1942. w. c. scHEu ETAL DRAFT REGULATING DEVICE FOR ORCHARD HEATERS 54 Sheets-Sheet 3 Filed Sept. 2, 1939 m gvwa/wbo/cs VWM/AM C. .5c/45u, .2E/wss E. CAMPBELL,

Patented July 2l, 1942 rss TENT OFFICE DRAFT REGULAT'ING DEVICE FOR ORCHARD HEATERS/ liam C. Scheu, deceased Application Septemberz, 1939, Serial No. 293,250

5 Claims.

This invention relates to temperature-controlled draft regulators for liquid fuel orchard heaters and is concerned particularly with heatresponsive devices for automatically establishing a-controlled influx of combustion air to the fuel vaporizing chamber of such a heater for normal burning operation thereof following the starting or ignition period of such a heater.

The heat-responsive draft-regulating device of this invention is primarily adapted for use with vaporizing type liquid fuel orchard heaters. In heaters of this type a vaporizing ame is maintained at or near the surface of the body of fuel contained in the heater to cause vaporization from the surface of this fuel. The oil vapors pass upwardly into a stack where additional air is mixed with them to cause substantially complete combustion of the vapors in a main name at a point removed from the vaporizing flame. A heater of this general type provided With such a stack forming a main combustion chamber is shown in U. S. Patent No. 1,930,863, issued October 17,1933, to William C. Scheu.

Heaters of this type are provided with one or more air-admitting openingsin the body communicating with the vaporirfiingy chamber to admit air to the vaporizing name in the vaporizing chamber. With such an arrangement it is preferable to supply a relatively large quantity of air to the vapcrizing chamber to support the vaporizing flame when the heater is first ignited and until the vaporizing chamber has been heated. After the vaporizing chamber has become heated and the main combustion flame is well established, a smaller amount of heat from the vaporizing flame is required to vaporize fuel; and if the air supply is not reduced to diminish the flame, there will be a tendency to vaporize an excess quantity of fuel. These relations are all a function of the heat generated in the Vaporizing chamber and are substantially independent of the temperatures existing where the main combustion takes place in the stack, or at any other place removed from the vaporizing flame.

In order to obtain proper and satisfactory operation of such a liquid fuel heater it is desirable to restrict the flow of air admitted to the vaporizing chamber after a sufficient quantity of heat has been generated therein. In many cases this operation is performed manually or not at all due to the labor involved. When this operation is not performed the heater consumes an eX- cess quantity of fuel and often smokes badly, thus wasting fuel.

for thevaporizing flame.

-A broad object of the invention is to .provide an improved heat-draft'regulating device for orchard heaters.

The principal object of the inventionv is to provide an'improved heat-controlled draft-regulating device for use in connection with a Vaporizing type of liquid fuel orchard heater, which is operable to provide a substantially unrestricted inflow of air into theY vaporizing chamber during a preliminary ignition period and to restrict automatically the admission of air to said Vaporizing chamber when the ignition is completed, in response to a temperature increase resulting from the heat generated Within the vaporizing chamber.

ofk theY heater, so as to thereafter maintain the relatively restricted admission of air to the chamber in quantities sufcient to maintain the desired normal burning rate during subsequent operation of the heater.

It is preferable to mount the draft regulating device in the opening which is 'also used to ll the heater with liquid fuel, as shown in the copending application of W. C. Scheu, Ser. No. 94,167, led August 4, 1936, and the cop'ending application of James R. Campbell, Ser. No. 235,299, led October 17, 1938, since no additional opening is then required for the admission of air However, it is preferable to have this opening substantially unrestricted when the heater is being filled with liquid fuel. the heater with a draft-regulating plate which is pivotally mounted on the heater adjacent one side of the opening and is shaped to conform substantially with the opening. Thusthe plate may-be swung back from a position extending over the opening, to a positionremoved from the opening, leaving the opening substantially unrestricted for filling purposes. This represents a decidedzimprovement over arrangements shown in said applications.l

Itis, therefore, a particular object of this invention to provide a draft-regulating plate for an orchard heater, which plate is normally in a position extending over'the air-admitting opening-in the heater during normaly burning operation thereof, and vis movable to another position removed from said opening and providing substantially unrestricted access to said opening.

Another advantagefmay begained by mounting the thermostatic means which providesthe automatic operation, on the draft-regulating plate and disposing it inwardly thereof. This removes the thermostatic means from within the air-admitting opening `when the .plate is swung For this reason we' prefer to provide back for the filling operation, thus removing an obstruction from the opening, and placing the thermostatic means in a position where it is less liable to be damaged. Furthermore, by placing the thermostatic means on the draft regulating plate and disposing it inwardly thereof, it is surrounded by the flame stabilizing baiile which is usually present in such heaters and is thus within the Zone in which the vaporizing name is burning. Hence the thermostatic means is primarily responsive to the temperature of the vaporizing name which is as desired.

Therefore, it is another important object of the invention to provide a heat-responsive draft regulating device for an orchard heater, with a draft regulating plate having a temperature responsive element mounted thereon and disposed inwardly thereof.

A further important object of the invention is to provide an improved form of adjustable limiting means for adjustably determining the position of the draft-regulating plate when it is in its air-restricting position.

Further objects and advantages of the invention, of which the above are typical, will either be specifically brought out in the ensuing description or will become apparent therefrom.

How the above, as well as other objects and advantages of our invention are attained will Abe more readily understood by reference to the following description, and the annexed drawings, in which:

Fig. l is a fragmentary vertical section through the base of a vaporizing type orchard heater provided with a draft-regulating device of our invention, the draft-regulating plate being shown in a closed or air-restricting position;

Fig. 2 is an enlarged fragmentary vertical section through the draft-regulating device taken on broken line 2 2 in Fig. 3, showing the draftregulating plate in an open or substantially nonrestricting position;

Fig. 3 is a plan view of the device taken along line 3 3 in Fig. 2, with the plate in an air-restricting position;

Fig. 4 is an elevational View taken along line 4 4 in Fig. 2, with the plate shown in substantially the same position as shown in Fig. 3;

Fig. 5 is an inverted partial plan View of the draft-regulating device taken on line 5 5 of Fig. 2, with the insulating cover over the bimetallic element removed;

Fig. 6 is a view similar to Fig. 5 of the draftregulating device, except that the draft-regulating plate is shown in an air-restricting position;

Fig. 7 is a plan view of a draft-regulating device showing a variational form of draft-regulating plate and adjustable limiting means;

Fig. 8 is a vertical section substantially along line 8 8 in Fig. 7, with the cover for the bimetallic element shown partly broken away and partly in elevation to illustrate the novel form of adjustable limiting means, this view being inverted and rotated to place the device in its substantially normal upright position so that the operation will be more easily understood; and

Fig. 9 is a vertical section through a further modified form of draft-regulating device according to our invention showing a plate utilizing the adjusting means illustrated in Figs. 7 and 8 operated by a bimetallic element which is located on the heater.

There is shown in Figs. 1 to 4 of the drawings a portion of a standard type of vaporizing liquid fuel orchard heater, indicated generally at I0.

The orchard heater comprises a bowl II which not only provides a base for supporting the upper structure but also forms a reservoir that contains a body of liquid fuel I2 which is vaporized in bowl I I and burned in the heater stack. Bowl Il is provided with a cover I4 which has a centrally disposed collar portion I4a around which the lower end of stack I5 ts snugly. The stack may be of any type suitable for orchard heaters, the exact kind being immaterial as far as the present invention is concerned.

The space I6 above the fuel body I2 and enclosed by the walls of bowl II and cover I4 constitutes a vaporizing chamber. A suitable opening, preferably circular, is defined by the raised collar portion I'I of cover I4 and is provided in order to admit air to the vaporizing chamber for maintenance of the vaporizing flame therein. This opening is preferably also used for filling the heater with liquid fuel and thus eliminates the provision of extra openings. A tight fitting weather cap IIb is shown covering the opening in full lines in Fig. l and in dot-dash lines in Fig. 2. rI'his cap is pivotally mounted to the cover I4 by loose-fitting hinge means IIc so that it may be slid upwardly out of engagement with the collar II and swung back away from the opening as shown in full lines in Fig. 2, during the burning operation of the heater. The collar portion I 'I also forms a mounting means for the draft-regulating device described later. A tubular member or flame-stabilizing baille I8 is preferably provided to facilitate the maintenance of a vaporizing flame within chamber I6 and extends downwardly from the periphery of the opening into the heater. The upper end of draft tube I8 is preferably provided with an outwardly extending flange which engages the inwardly turned flange on raised collar I'I as shown to support the draft tube, which extends downwardly from the wall ofcover I4 into the oil body I2 as illustrated in Fig. 1, The upper end of draft tube I8 is open for the admission of air which enters the vaporizing chamber through the draft tube. A suitable wick I9 is preferably provided adjacent the upper end of tube I8, the wick member taking any suitable form, such as the body indicated, and is preferably of fibrous asbestos or other porous material. The wick is preferably wrapped or enclosed in a foraminous metal envelope 28 which holds the wick in place and yet permits access of oil to the lower portion of the wick..

As may be seen best from Fig. l, draft tube I8 is provided with a notch 22 just beneath the top flange at the lower or left-hand side as viewed in Fig. 1. A short lug 23 projects inwardly through notch 22 from the rim of collar I'I. This construction not only assures that the draft tube will be inserted through collar II and maintained in the proper position, but the lug also locks the draft tube tocover I4 against accidental removal. Of course, other forms of `construction can `be used for this purpose.- As may be seen by inspection of Figs. l and 2, the draft-regulating tube is slotted at I8a and I8b so as to allow the products of combustion and the vapors to pass out into the heater. The slot I8b stops short of the top of the draft-regulating tube, ywhile the slot I8a is shown extending clear to the top thereof to provide for the removal of this tube when the draft-regulating device is in place. The fact that the slot ISa runs clear to the top of the draft-regulating tube allows the tube to be contracted when it is inserted within the opening defined by the collarv II, so that tion may be somewhat widened for this purpose,

as shown at 28h in Figs. 2V and 3. The draftregulating device is further shown as comprising a bimetallic thermostatic element 33 enclosed within an insulating housing Si which is mountedV on'the drafteregulating plate Zt'and is dis- 20.

posed inwardly thereof, and is adapted-to effect closure olf'the draft-regulating plate.

TheV thermostatic control means, which may comprise the coiledjbi-metallic element Sil, is attached'in any suitable manner at one end to a bracket 31, which bracket is attached to the plate 28 :by any suitable means, as by screws, andis preferably heat insulated from direct engagement with the plate by a layer of insulation 38, as best seen in Fig. 2, and may be heat-insulated from the screws by a second layer of insulating material Saa, as may be best seen in Figs. 5 and 6. These strips of insulating material retard the rate of heat-transfer to the thermostat.

Bimetal strip 30 curves through almost one complete turnor circle, being curved in a plane parallel to the plane ofplate 28; and when it is cold, the strip occupies a `position as shown inFig. 5. In this, position, it is engaged by a relatively xed holding member All, which is securedvto the, heater adjacent the opening formed by the collar l'l and maybe formed as a part of the same stamping or may be made of heavier material. Thek member it projects downwardly from the heater in such manner that the end of the member bears against the side of .bimetallic element 3); Engagement of holding member 46j with the bimetallic element holds plate 281 raised in its rst or upwardly tilted position extending over the opening, illustrated in Fig. 2,V in which position relatively free passage of air through the opening is afforded.

In response tok heat generated by the Vaporizingmflame within Vaporizing chamber i6, bimetalli/cV element straightens out somewhat and reachesra .position similar to that illustrated in Fig.l 6, and moves out of engagement with the member Ml. Whenthe bimetallic element 3d disengages from the member 40, plate 28 drops suddenly under the inuence of gravity to a lowered` position extending over the opening, suchwas shown in Figs. 1, 3 and 4, in which it restrictsthe passage of air through the opening provided by the collar i1. In the extreme lowered position, such as shown in Fig. 1, the edge of theplate 23lies against the inwardly turned ilangeportion of the collar I7, in which positionthe supply of air to the vaporizing flame is substantially cut olf, except for that which flows through a notch 41 which may be provided in the plate. 28 rfor this pur-pose.

Itiispreferable that the plate- 28 be not alldwedto reach theextreme lowered position and that its-downward movement, be limited to Y a positionl such as/shown. inFig. 4', in whicnthe opening is notI entirely closedland. theV plate is. spacedfromV theftop-of. the-collarl l1. For. this, purpose I m-ay provide Aadjustable .limiting means. comprisinga-member movable ktodifferent .positions, which may include, for example, an adjustablevlimiting member 50,1. which is rotatably mounted about a pivot pin 5I. which may .be secfuredto the plateZB in any desired manner. A coil'spring 52 isshown encircling the pin 5|y and is held thereon by flange portion 5Ia of theV pin andV is adapted to biasthe limiting means. Silagainst the plate28.: so that it maybe held` in any desired rotative position by friction. The limiting means 50is provided'with-an upturned handle portion i3Y which mayY be graspedY for-- manual engagement todetermine the rotative ,position ofthe limiting means 5l) and may also be used asa handle to-swing the plate 23lin a. Counterclockwise direction (when viewedin Fig. 2) to another position removed romfthe opening ldelinedby'the collar Il' tothusleave thisopeningsubstantially unobstructed. 'Io provide fory the limiting of the movement of the plate 28, astop member in the form citan opstanding rampy 54 is positioned adjacenty the opening and is adapted to cooperate with the limiting member 50'. The inclined portion of the ramp which is adaptedfor engagement by the limiting ymember Eil-comprises portions which are located at successively different distances from the plane of the opening dened-'by the collar i1, and this plane is probably best defined by the plane ofthe top of the raisedcollar portion l?.

It should be obvious that as the'limiting member 50 is rotated clockwise, as viewed in Figs. `2 and 4, to dii'erent positions and in contact with the ramp 54, the restriction imposed by the plate 23' increases. This adjusting or limiting arrangement is entirely comparable to that shown in the above-mentionedScheu application.

The stop member 51% may conveniently be formed as a part of the same stamping as the .collar member i. When it is constructed' in such a manner, it is :preferable to notch the plate 28, as at 55, to provide clearance for the ramp.

Bimetallic element 3d is preferably enclosed -within housing 3|, noi-l only to protect the yelement against physical injury, but also to insulate this element from the vaporizing flame and thus properly delay the response of the thermostat to heat received from the llame in chamber i6. For this reason, the interior walls of housing 3| are lined with a layer of insulating material 4g, such as asbestos or the like.

The operation of my improved draft-regulating device will now be described briefly. 'Ille reservoir is first filled with a body of liquid fuel I2 to the proper level. This may be accomplished by moving the weather cap I'Ib from its dotdash position shown in Fig. 2 to4 some such position as shown in full lines in Fig. 2. The plate 23 is then swung back away from the opening, as by grasping the handle 53 and swinging the plate in a counterclockwise direction, as viewed in Fig. 2. By using a plate which substantially conforms to the shape of the opening and mounting it pivotally adjacent the edge of the opening, the opening is practically unobstructed when the plate is swung back in the abone-described manner. The heater' is` then filled with fuel through this opening. The attendant then inserts the tip of his lighting torch in the openingV and Adischarges a suitable rquantity of burning.. ignition fluid, which .may comprseL mixture of gasoline and kerosene or the like, through the opening onto wick I9. A portion of .this burning fluid falls down upon the surface of fuel body I2. The ignition fluid, burning on the surface of fuel body I2 and around wick I9, establishes a vaporizing ame which heats the liquid fuel sufliciently to effect generation of fuel vapor therefrom, and this vapor is carried into the stack I by the draft through the vaporizing chamber. The main vaporizing llame is established within the tubular member comprising the balile I8 and the vapors therefrom pass into the body of the heater through the slots I8a and ISU and thence into the stack I5. When the rate of evolution of fuel vapors is adequate, the main combustion flame of the heater is established Within or above the stack assembly I5, and it will be understood that some ignition fluid may be poured into the stack to facilitate ignition of the fuel vapors within the stack.

After the tip of the lighting torch is removed from the opening, plate 28 is manually rotated clockwise to the position of Fig. 2 in which the holding member 40 engages the side of bimetallic element 3D. In this first operating position, regulating plate 28 is raised to a position affording relatively free passage of air through the opening, and the limiting member 50 is positioned above the stop member 54. The plate 28 is gravitybiased in the first position toward a closed or second position and is held in this rst position, by engagement of holding member 4B with bimetallic element 3i, against gravity, Which tends to move the plate clockwise into a second or closed position in Which the passage of air through the opening is more or less restricted. All the time the regulating plate is held in this rst position, a relatively large amount of air is admitted to the vaporizing chamber, and the vaporizing flame burns at a relatively high rate. The heat from this vaporizing flame is transmitted to bimetallic element 3D by conduction and radiation from the metal parts of the draft tube and regulating device, and in response to this heat received, thermostat 3E) tends to straighten out.

The curvature of the thermostat is preferably such that all movement of the free end thereof is substantially perpendicular to the path of movement of plate 28 and is transverse to the end of the holding member 40, and consequently the straightening movement of the thermostat, While engaging the member 40, causes substantially no movement of the draft-regulating plate 28. Eventually the quantity of heat received by bimetallic element 3l) is such that the free end of this element moves past and disengages from the end of the holding member 48, reaching some such position as shown in Fig. 6. As the free end of bimetal strip 38 moves past the end of the member 4t, out of engagement with said member, plate 28 drops under the inuence of gravity to its second operating position in which the flow of air through the opening is restricted to a greater or lesser extent according to the amount of closure permitted plate 28. As previously described, this closure is determined by the rotative position of the limiting member 5l), since this member cooperates with the ramp 54 to stop the plate 28 after it has been released by the thermostatic element.

With the plate now in its second position, as shown in Fig. 4 for example, it restricts the passage of air through the opening and the vaporizing llame is reduced in size and ability to vaporize fuel as Aa consequence of its reduced air supply, and under these conditions the main llame in stack I5 is also reduced. Obviously, by rotating the limiting member 50 clockwise, it will move up the ramp 54 and decrease the restriction placed on the admission of air by the plate 28, and by rotating it counterclockwise it will increase its restriction. More fuel will be Vaporized as the restriction is decreased and as a consequence the main combustion ame will burn higher or lower in accordance With the restriction. In any event, the air admitted through the opening is less than that admitted when the draft plate is in its original position for admission of the maximum amount of air to the newly lighted flame and before the draft plate has been released by thermostat 30 in response to heat received from the vaporizing flame.

The rate of heat transfer to thermostat 30 depends upon the quantity and efficiency of the insulating means 38 and 49 within housing 3|; and the period of time required for the thermostat to release the plate 28 may be increased or decreased respectively by increasing or decreasing the amount of insulation within the housing. The insulation preferably entirely surrounds the bimetal strip, or substantially so. For any particular type of heater, the correct amount of insulation may be determined by experiment, and should be made such that the maximum amount of air is admitted to the vaporizing flame for a suflicient time to insure an adequate heating of the fuel body and the generation of an adequate amount of fuel vapor within the chamber I6. A slot is cut in one Wall of housing 3| to permit the holding member 40 to operate through this Wall.

After the fire in the heater has been put out by extinguishing the vaporizing flame, the thermostat 30 cools and tends to return to its initial position as shown in Fig. 5. However, as Will be seen from Fig. 6, the bimetallic element cannot do this since its free end now comes into contact with the side of the holding member 40. After this engagement, continued cooling of the bimetallic element does not change its position, but merely causes it to press lightly against the side of member 40; and because of the circular shape of the thermostat, no damage is done to it since the pressure is not sucient to cause any permanent deformation of the bimetallic element. The parts remain in this position until it is desired to again light the heater, at which time draft plate 28 is lifted, as previously described; and the act of lifting the draft plate disengages the thermostatic element 30 from the holding member 40 so that the former can spring back to its normal position when cold, that is, the position shown in Fig. 5. When the draft-regulating plate is again lowered to its first operating position, member 40 comes into contact with the side of thermostat 30, and the draft-regulating device is reset to repeat the cycle of operations pre-y viously described. The plate 28 may be lifted by grasping the portion 53 of the limiting member 50.

The coiled shape of the thermostat 30 is of definite advantage in preventing injury to this element. In the event that regulating plate 28 should be forced downwardly when it is occupying the starting position shown in Fig. 5 with the bimetallic strip engaging the holding member 40, no damage is done to the part because the bimetallic element has suiicient resilience to yield and allow the plate to be pushed down into contact with the periphery of the opening, as shown in Fig. 1 for example. Movement of this type simply causes the thermostat to be forced into a coil of smaller radius without causing any harmful or permanent deformation of the thermostat which would impair its operation. The thermostatic means shown and described hereinis disclosed and claimed in the abovementioned Campbell application and is used herein for the purpose of example, and it should be understood that the draft-regulating devices of this invention are not limitedl to this particular type of thermostatic means.

Referring now to Figs. 'l and 8, there is illustrated aregulating device embodying a type of adjustable limiting means-of our invention, which is highly advantageous W-ith this arrangement theheater cover Hl is provided with an upstanding collar B0, which is-comparable to and used for the same purpose as collar I-1 shown in Figs. 1 4. Pivotallyv mounted on the heater adjacent the opening dened by collar Gil-is a draft-regulating plate 61 of any convenient shape, although it is shown as substantially circular. The pivotal mounting 62 for this plate is shown attached to the collar 60 and for convenience is secured to-an enlarged portion of an inwardly extending flange 63V provided on said collar. A thermostatic element'd isrshown secured to the plate 6I and disposed inwardly thereof in'V the same manner as the element 3l in Fig. 2'for example. A cooperating holding member 65 is shown secured to the heater in the samemanner as holding member Ml of Fig. 2. A suitable slotted tubular member 66' comprising the customary draft-regulating tube is shown extending ,downwardly from the periphery of the opening defined by the collar (50V and is supported in this position in any convenient manner. VFor example, the collar 60 may be provided with two or more inwardly extending pins 6] and the regulating tube may be provided with a similar number of notches (iB-in the rolledover` upper portion thereof so that the'notches and pins may be alined to bring the rolled-over edge ofthe tube 66 into engagement with the under side of the inwardly projecting, portion 63V of the collar B0. After the tube has been brought into this position it may be rotated with respect tothe collar 60 so that it will be supported by the pins.61,.as shown in Figs. '7 and 8.

In this form of our inventionthe relatively fixed stop member islocated adjacent the opening and has a surface extending subtsantially parallel to the plane of the opening. A portion ofthe flange 63 may be advantageously utilized for'thispurpose. This flange'portion used as a stop member is designated as 69, and it will be seen that it hasl asurfaceY which extends substantially parallel to the plane of the opening. This surface is engageable by an inwardly projecting portion 'H of a rotatable and adjustable limiting member 1-2 which is rotatablysecured to the plate 6I by'a pin 13 and is biased against the plate by a spring 14 in the same manner as the adjustable limiting member in Fig. 2. This limiting member is rotatable to diiferent positions to determine the position of the plate when the'inwardly projecting portion 'il of limiting member is in engagement with the surface 69.

The plate is shown in full lines in Fig. 8 in a second or air-restricting position. Its first or air-admitting position may be substantially the same at that shown for the plate 28 in Fig. 2 and it may be held in its first position by the coactin ofthe thermostatic means 6l!Y and the holding member 65 in the same manner as in the forms previously described.

Rotation of the adjustable limiting means 12 to bring the inwardly projecting member 'H nearer the hinge means 62 raises the plate El and thus reduces the air restriction imposed thereby. The result of such a change in position of the limiting member is shown in dot-dash lines in Fig. 8. It should now be obvious that movement of the limiting means 12 so as to move the inwardly projecting portion H (counterclockwise as shown in Fig. 8) along the surface 69 in a direction away from the hinge means 6'2 will lower the plate 67| and increase the restriction on the incoming air imposed thereby. The plate 6l is provided with a notch 18 in which the inwardly projecting portion 1| is free to travel, and this notch may be used to define the limits of movement of this portion and consequently limits the rotation of the rotatable adjusting means, since inwardly projecting member 1I may be positioned so as to engage the ends of said notch. A cooperating notch 15 is also provided in the flange E3 at the end of the surface 69 so that the inwardly projecting portion 1| may project through this notch at one limit of its rotational path and allow the plate 6l to come in close engagement with the flange 63.

The rotatable limiting means '52 may be provided with an outwardly extending or upstanding handle portion 1B which may be manually grasped to adjust the rotative position of this limiting member. This handle may also be used to set the plate in its first position and also'to swing the plate back from the opening to leave the opening unobstructed for filling purposes. Indicating means may be provided on one end of the limiting member I2, which means may comprise a pointer portion 'il adapted to mask one or more spaced slots provided in the plate 6l. During operation of the heater, the Vaporizing flame is visible through these slots and the position of the pointer 'Il may be ascertained by noting the particular one or ones of the slots which it masks.

It should be obvious that the adjustable limiting means illustrated in Figs. 7 and 8 is not necessarily used with a circular plate as illustrated but is applicable to substantially any shape of plate. Furthermore, this arrangement is not necessarily limited to the particular type of thermostatic operating means shown but may be used with any desired type of operating means.

A variational arrangement of the cooperating holding and thermostatic means is illustrated in Fig. 9. In this figure the plate M is shown provided with a depending holding member 8| which is secured thereto, and extends inwardly thereof, and passes through one of the slots in the draft tube 66, the slot being somewhat enlarged over that shown in Fig. 8 to accommodate this holding member. In this form of our invention the thermostatic means, such as the thermostatic means 64, is secured to the heater and is disposed Within the heater in heat-receiving relation to the vaporizing flame. The holding member 8| passes through a slot provided in the side wall of the thermostatic means 64 and engages bimetallic element 64a which acts to hold the plate in its first position. In Fig. 9, the plate is shown in its seccnd or air-restricting position, however. Obviously, other forms of thermostatic elements may be substituted for the thermostatic element 54 in Fig. 9. Although I have shown the plate 6l provided with the rotatable limiting means 72 of the form shown in Figs. 7 and 8, it should be appreciated that the form of limiting means shown in Figs. 2-4, or other forms of limiting means, may be substituted therefor.

It should be understood, also, that the feature of mounting the thermostatic means inwardly of the draft-regulating plate as shown in Figs. 1 8, is not necessarily restricted to a substantially circular draft-regulating plate but may be used with draft-regulating plates in general irrespective of their shapes. Obviously this mode of mounting the thermostatic means may be practiced with other forms of thermostatic means than the example shown herein. Furthermore, this feature is obviously independent of the particular type of limiting means employed.

Having described certain preferred embodiments of our invention and certain modifications thereof, We wish it understood that various changes in the shape, construction, and arrangement of the various parts may be made without departing from the spirit and scope of our invention. For example, the regulating plate may be mounted on a collar which is removablysecured to the collar Il of Fig. 1 for example, or the plate may be otherwise removably secured to the heater rather than directly mounted on the heater. Consequently, it is desired that the foregoing disclosure be considered as illustrative of, rather than limitative upon, the invention set forth in the appended claims.

We claim:

1. A heat-responsive draft-regulating device for an orchard heater having a vaporizing ame within the heater and provided with an opening for admitting air to maintain saidA vaporizing flame, which comprises: a draft-regulating plate pivotally mounted on said heater adjacent said opening and movable between a rst position affording relatively free passage of air through said opening and a second position restricting passage of air through the opening, said plate being biased toward the second position; and thermostatic means mounted on said plate and disposed inwardly thereof and in heat-receiving relation to the vaporizing flame within the heater, said thermostatic means comprising a bimetallic element curved in a plane parallel to the plane of the plate and adapted to hold the plate in the first position and operable in response to heat generated by said vaporizing flame to release the plate and permit the plate to move into said second position.

2. A heat-responsive draft-regulating device for an orchard heater having a vaporizing flame within the heater and provided with an opening for admitting air to maintain said vaporizing flame, which comprises: a draft-regulating plate pivotally mounted on said heater adjacent said opening and movable between a first position affording relatively free passage of air through said opening and a second position restricting passage of air through the opening, said plate being biased toward the second position; thermostatic means disposed in heat-receiving relation to the vaporizing flame within the heater and adapted to hold the plate in the first position and operable in response to heat generated by said vaporizing flame to release the plate and permit the plate to move into said second position; a relatively fixed stop member located adjacent said opening and having a surface extending substantially parallel'to the plane of said opening; and an adjustable limiting member rotatably mounted on said plate, said limiting member having a portion projecting inwardly of said plate and engaging said surface when said plate is in said second position, said limiting member being rotatable to diierent positions to determine the position of said plate when said portion is in engagement with said surface.

3. A heat-responsive draft-regulating device for an orchard heater having a vaporizing name within the heater and provided with a substantially circular opening for admitting air to maintain said vaporizing llame, which comprises: a substantially circular draft-regulating plate pivotally mounted on said heater adjacent one side of said -opening and movable between a first position aifording relatively free passage of air through said opening and a second position restricting passage of air through the opening, said plate being biased toward the second position; thermostatic means disposed in heat-receiving relation to the vaporizing ame within the heater, said thermostatic means comprising a bimetallic element adapted to hold the plate in the first position and operable in response to heat generated by said vaporizing flame to release the plate and permit the plate to move into said second position; a relatively xed stop member l0- cated adjacent said opening and having a surface extending substantially parallel to the plane of said opening; and an adjustable limiting member rotatably mounted on said plate and adapted to engage said surface of the stop member when the plate is in said second position to determine the position of the plate and the restriction imposed by the plate on passage of air through the opening, the limiting member being rotatable to different positions to vary the position of the plate when the limiting member engages said surface.

4. A heat-responsive draft-regulating device for an orchard heater, which comprises: a body member having an air opening; a draft-regulating plate pivotally mounted on the body adjacent said opening and movable between a first position affording relatively free passage of air through the opening and a second position restricting passage of air through the opening, said plate being biased toward the second position; a fixed holding member mounted on the body; and thermostatic means mounted on the plate in a position to engage the holding member and hold the plate in the first position, said thermostatic means comprising a coiled bimetallic element having a free end that engages said holding member and is movable in response to heat generated by the heater to disengage the holding member and permit the plate to fall freely into the second position, the bimetallic element being so positioned that movement of the free end of the element at the point of said engagement is substantially at right angles to the path of movement of the plate at that point and causes substantially no movement of the plate during engagement with the holding member.

5. A heat-responsive draft-regulating device for an orchard heater, which comprises: a body member having an air opening; a draft-regulating plate pivotally mounted on the body adjacent said opening and movable between a first position affording relatively free passage of air through the opening and a second position restricting passage of air through the opening, said plate being biased toward the second position; a fixed holding member mounted on the body; and thermostatic means mounted on the plate in a position to engage the holding member and hold the plate in the rst position and heat operable to move in engagement with the holding member before reaching a position out of engagement with the holding member, said thermostatic means comprising a coiled bimetallie element having a free end that engages said holding member and is movable in response to heat generated by the heater to disengage the holding 

